This invention relates to enhancement of a received signal to remove distortion components of a transmitted signal, and more particularly to cancellation of intermodulation distortion in a radio-frequency transceiver.
Some communication systems provide the capability of transmitting and receiving at the same time. In radio frequency communication, a transceiver may transmit in one radio frequency band while receiving in another radio frequency band. Some such systems are referred to as frequency-division duplex (FDD) systems. When the two bands are sufficiently separated in frequency, the transmitted signal may not interfere significantly with the received signal. However, in part due to non-linear characteristics of circuit components in the transmit and receive paths and/or coupling of those paths, some of the transmitted signal may nevertheless “leak” into the received signal. Although the level of such leakage may be low, the error rate of information decoded from the received signal may be adversely affected. There is therefore a need to mitigate the effect of such leakage to improve characteristics of the communication system.
One approach to dealing with non-linearities in a transmitter, for example resulting from non-linear characteristics of a power amplifier, is to predistort a transmission signal. Although such predistortion may mitigate some of the leakage between the transmitted signal and the received signal, there is a need for further mitigation of the effect of the leakage.